9-patch - 1px border is blurred

You should use 9-path tool for each png in different drawable folder. Sometimes problem is this the Android try to convert the png and blur the black lines, what cause later problem with properly displaying.

To circumvent this problem simply drop the 9 patch inside the drawable-no-dpi folder. This allows to have one image for all densities. And android won't touch the image.

This is mostly what I do for my projects, unless I really want to have a difference between the densities. In that case, I create one 9-patch per density.

Alternate solution:

Shrink your top and left markers by 1 pixel on each side. This will ensure that scalable part does not overlap the grey border.